Vibration damping in motor vehicles



Aug, 11, 1942.!

w. H. IBAGLEY, JR., Erm. v1BRA TIoN DAMPING 1111101011 vzaxm'zlfrzs Filed Aug.` 1s, 195e 'y mzzl-gm ff Patented Aug. 11, 1942 uNiTED STATES PATENT OFFICE vmaa'rlou mimmo 1N Moron vEnroLEs William H. Bagley, Jr., and Thomas W.` Halloran,

Detroit, Mich., asffnors to Composite Materials Corporation, Detroit, Mich., a corporation of Michigan Application August 13, 1938, Serial No. 224,678

"16 Claims. (Cl. 26o-4) This invention relates to damping or deadening oi vibration in vehicle bodies. j

The principal object of the invention is to im prove the art of vehicle body commotion.

A further object is to provide eeotlve and economical means for damping vibration to prevent breakage due to crystallization of metals or loosening at seams or similar connection.

Another object is to reduce rapidly the intensity of vibrations of metal parts in order to minimize the occurrence and transmission of sound.

A further object is' to provide a vibration deadening or damping material which may be applied to metal parts by a spraying process.

Another object is to provide a vulcanizable material, reduced by a solvent for purposes of application, which can be applied to the metal body and cured simply by air drying or by more rapidly drying and vulcanlzing the material under the iniiuenoe of heat involved in the baking prooess generally employed for curing the paintV4 lacquer, or enamelfmishes on such bodies.

A further object is to provide a vibration damping material which may be applied cold.

Another object is to provide a vibration damping material which is clean and non-corrosiveto handle, which adheres tenaciously to metal over a wide range of temperatures and which will not aect paint,l lacquer, or enamel iinishes.

A further object is to provide a damping material which dissipates vibration more rapidly, hasl greater rigidity, strength, and wear resistance, than compositions heretofore used for similar purposes. y

Another object is to provide a novel method of eecting damping or deadening of vibration in a vehicle body construction.

Other objects, features, and advantages, will become apparent from the following description and appended claims. l

For the purpose of illustrating the genus of the invention, a, concrete embodiment in the form of an automotive vehicle body is shown in the accompanying drawing treated according to the principle of this invention.

in the drawing:

Figure l is a central longitudinal section through an automobile body; y

Fig. 2 is an enlarged horizontal view taken substantially on the line 2-2 of Fig. 1; and

Fig. 3 is a graph showing comparative characteristics of different types of ySound deadening material.

Referring to the drawing, Figures 1 and 2 depict one specific embodiment of the present invention in the form of an automobile body 5, the -sheet metal panels 6 of which are coated on the interior surface thereof with a vibration damping material 1. This material is adapted to be applied to the interior surface of the metal panel t by spraying or similar process of application and largely eliminatesnoise and breakage by preventing drumming or rumbling of panels and -rapidly damps vibration of such panels to prevent crystallization of metal and consequent breakage at or adjacent seams or similar welded or soldered connections, such as indicated at 8. The sound proong -and vibration damping material, according to the present invention, consists broadly of a rubber compound including mineral and organic llers,'which is reduced in viscosity by being out back by a suitable rubber solvent, such as benzole or rubber naphtha so that it may be employed by spraying, and includes vulcanizing and y vulcanization accelerating agents, so that it can be cured by the usual heat treatment for the finishing material 9, such as paint, lacquer, synthetic enamel, and primers, or simply cured in air when properly compounded with the correct vulcaniz'ing and accelerating agents. The coating material consists primarily of rubber, an organic filler such as a coumarone type resin, a rubber solvent, such as benzole or rubber naphthas, which are also'solvents for the resin, ordinary clay, or similar colloidal material, l

a moderately fine sand, and a small quantity of a vulcanizing agent such as sulphur, and small quantities of one or more vulcanization accelerating agents. These materials are preferably employed in the following approximate 'proportions by weight:

Per cent Rubbery 4.35 Coumarone resin 17 Solvent 11.2 Clay 23.8 Sand 43 Stearic acid 0.167 Zinc oxide 0.21 Sulphur 0.2i Accelerators 0.07

The proportions of the essential ingredients may be varied within about the following limits:

Rubber 3 to 6 Resin i 15 to 2o Solvent 9 to 14 Clay 20 to 26 Sand 40 to 46 Vulcani'zing and accelerating agents 0.25 to 0.92

The rubber in the abovecompositions may be any of the commercial grades of plantation rub- -ber or plantation para in any of its commercial,

indicated, the solvent may be desired rubber solvent. Practically any ordinary types of clay and sand may be employed. In conjunction withthe accelerators employed, a small quantity of.

' employed, although this may be replaced by a slightly increased quantity of the sand. Zinc oxide adds to the rigidity oi.' the product. Preferably a number of accelerators are employed to take care of different temperature conditions involved in curing lacquer, primers, and baked en amels, so that the coating material will beadaptable for varying conditions of commercial practice. Lacquers areY normally baked at temperatures of from 175 to 200 F., primers at about 200 to 225 F., and baked enamels at from about 275 to 325 F. One accelerator which may be employed consists of approximately 25% by weight, meta-toluylene diamine, 50% phenyl-alpha-naphthylamine, and 25% stearic acid. This accelerator is known under the trade name Neozone. Another vulcanization accelerator which may be employed is. known by the trade name Zenite and is a zinc salt of 2-mercapto benzothiazole. A third accelerator preferably employed, especially where the coating material is to be vulcanized during the baking period employed for curing baked enamel, is -a tetramethf-` 35 yl thiuiam monosulphide. When baking temperatures ranging from 275 to 325 F. are not to be encountered, this vulcanization accelerator, l

known by the trade name Thionex may be omitted. In the ilrst example embodiment above mentioned, the ilrst described accelerating agent alone may be employedjf desired.

Another commercial embodiment of the coating material may take approximately the follow- A third embodiment of the present coating material may consist approximately of the following proportions by Weight:

Per cent Rubber 4.75 Resin 17.6 Solvent 12.4 Clay 23.6 Sand 40.7 Stearic acid 0.21 Y Zinc oxide 0.28 Sulphur 0.28 Zenite 0.086 Neoone 0.086 Thionex 0.0086

The mineral llers, clay and sand, especially 60 thickness of coatings.

distribution ot the resin and prevents Segregation of the same. The sand acts as a weighting agent as well as enhancing the strength, wear resistance qualities, and rigidity ot the product.

5 The organic illlers, such as the synthetic resin and Stearic acid, when the latter is employed. lend cohesiveness to the coating material and combine physically with the mineral iillers employed to give body and rigidity to the coating material.

Heretofore, coating materials employed for a similar purpose generally have an asphalt base and include such fillers as asbestos, resin, dryins oils, wood or cork flour, and a dryer. The

main disadvantages of such a type ofsounddeadening and vibration damping material reside in the use of the asphalt base which makes the composition dirty or smutty, has a tendency to damage paint and prevent the paint or similar nishing material from adhering properly to since the latter has an initial durometer hardness at room temperature of from about 50 to 60, while the present material has a hardness on the same scale of from about 75 to 90. This increased hardness is desirable'since it increases o the rapidityV with which the material will dampen or deaden vibration and enables the material to eiectively seal joints and function as an`anti squeak material at certain joints. Y The present material retains its `form and adheslveness to metal from temperatures weil below F. to about 200 F. temperatures.

The intensity o! sound depends upon the en- `ergy of the wave motion producing such sound. The decibel is the usual unit for measuring the o loudness of sound. In telephone practice, it is equivalent to the loss in power in one mile of standard cable at 860 cycles: A diierence of one decibel is approximately the smallest change in volume of sound which a normal ear can detect. If a wave motion of a certain arbitrarily chosen intensity is set up in a unit area panel covered by a sound deadening coating, and the coating allowed to dampen the wave motion, the time in seconds required to eiIect a certain decay in wave intensity measured in decibels will ailord a scale for comparison of the dampening eiect of such sound deadening material. Fig. 3 is a plot showing curves for asphalt base materials of the prior art and rubber base materials of the present invention and shows times in seconds required to effect a 95'decibel decay in the intensity of the wave motion, as above indicated, to aiord a comparison of the dampening eiIect o! the above indicated materials for different In this plot, both the weight in pounds per square foot of coating applied to a plate and the thickness of such coating in inches are plotted along the abscissa as an axis and the decay time, measured in seconds e5 when a wave motion of a certain arbitrarily chosen intensity is set up in a unit area panel and diminished by the speciiied amount, suchtime being plotted with reference to the ordinate axis.

In automotive vehicle body practice, the time for such reduction in intensity of the intensity of the wave motion should be below about 12 to 15 seconds. It will be noted in connection with the rubber base material that coatings as thin as %lths of an inch will produce the desired damping the colloidal material, clay, aids in maintaining eect. It will be noted that the asphaltbsse material requires a coating of more than twice that thickness in order to effect the same results. It

will also be noted that the asphalt curve turns up quite abruptly when coatings less than 2nd of an inch are employed showing little or no damping. Thus, the sound deadening or vibration deadening effect of an asphalt base material is apparently due practically solely to its weight. On the other hand, the rubber base material for thicknesses between 1/th and %4ths o! an inch, having a weight in pounds per square foot of from .4 to .9 of a pound, gives quite uniform resuits, so that sound dampening must depend upon other factors such as hardness, rigidity, and strength kof the rubber base material and not primarily upon its weight. The present material attains its hardness, rigidity, strength, and elas- 5. A vibration damping cohesive, viscous and hardenable mass comprising approximately from to 20% of a coumarone resin; from approximately 9 to 14% rubber solvent; from approximately 60 to '72% inorganic iiller and the balance including rubber in an amount not greater than 6%.

` 6. A vibration damping cohesive, viscous and hardenable mass comprising approximately from 15 to 20% of a coumarone resin; from 9 to 14% rubber solvent; a major proportion of inorganic filler and in no event less than 60% and the balticity during the vulcanization process and may attain the same during a simple air drying .if proper vulcanizing and vulcanization accelerating agents are employed in the correct proportions.

Although several embodiments of the invention have been above indicated, it is to be lunderstood that various'changes in the proportions of the ingredients and in the ingredients themselves, as

well as inthe methods of applying the composi- ,p

tion, may be made vwithout'departing from the spirit and scope of the invention, as dened in the appended claims.

What'is claimed is:

1. A vulcanizable viscous homogeneous mass comprising approximately from 36% rubber. from 15-20% of a coumarone resin, from 944% rubber solvent, and from 60-72% inorganic filler.

2. A vulcanizable viscous homogeneous mass comprising approximately from 3-6% rubber; from 15-20% of a coumarone resin, from 944% rubber solvent. from 4046% sand, from 2li-26% clay, and from 2%00 of 1% to 9%00 of 1% vull canizing and vulcanization accelerating agents.

3. The method ofdamping vibrations in a relatively thin panel subject to vibration which comprises applying to a surface or said panel a coating of a viscous homogeneous vibration damping mass comprising appilmately from -6%l rubber, from 15-20% of a coumarone resin, and from 944% rubber solvent, from 6072% inorganic ller.

4. The method of .damping .vibrations'in a 'relatively thin panel subject to vibration which comprises applying to a surface of said panel a coating oi a viscous homogeneous vibration damping mass comprising approximately from 36% rubber, from 15-20% of a coumarone resin,

from 9-14% rubber solvent, from 404696 sand,l

ance including rubber in an amount not greater than 6%.

'7. A vibration damping cohesive, viscous and hardenable mass comprising a major proportion by weight of inorganic filler, of not less than approximately by weight of the composition; a binder for the ller in such an amount as to provide a cohesive hardenable composition having vibration damping properties, the said binder comprising a coumarone resin and rubber not exceeding approximately 26% `by weight of the total composition, and a rubber solvent present in an amount sufficient to render the composi` tion viscous and applicable to a surface.

8. The composition as deiined in claim 'l in which rubber is present in an amount not greater than approximately 6% by weight of the composition.

9. The composition as dened in claim "l, in

13, The composition as deiined in claim 7 in,

which the 'binder includes coumarone resin ina proportion greatly exceeding that of the rubber. 14. The composition as dened in claim 7 in l which the binder includes a predominant prooi' 1% vulcanizing and vulcanization accelerating l agents.

portion of a coumarone resin.

15. The composition of claim position is vulcanizable.

16. The composition of claim 7 having added thereto a vulcanizing and vulcanization accelerating agent.

WILLIAM H. BAGLEY, Ja. THOMAS W. HALLORAN.

'l but which com- 

